The role of glucose-1,6-P2 in regulation of metabolism is to be studied. The enzymes that synthesize and degrade glucose disphosphate need further characterization. The former is shown to be a phosphoserine enzyme requiring magnesium and inhibited strongly by fructose diphosphate, acetyl CoA and citrate. Inhibition by citrate suggests that glucose-diP is a positive signal for energy production by glycolysis. The nature of this inhibition will be studied. The mechanisms of glucose-diP hydrolysis will be studied. The relation of the Pase to the synthase will be determined. The enzyme from brain is known to have a low Km, Mg2-ion requirement, and a neutral pH optimum.